Department of Joint Disease Research, 22nd Century Medical and Research Center, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.AbstractBACKGROUND:

The present study sought to identify dietary nutrients associated with the prevalence of radiographic knee osteoarthritis (OA) in the Japanese elderly of a population-based cohort of the Research on Osteoarthritis Against Disability (ROAD) study.METHODS:

From the baseline survey of the ROAD study, 719 participants >or=60 years of age (270 men, 449 women) of a rural cohort were analyzed. Dietary nutrient intakes for the previous 1 month were assessed by a self-administered brief diet history questionnaire. The radiographic severity at both knees was determined by the Kellgren/Lawrence (KL) system.RESULTS:

The prevalence of knee OA of KL >or=2 was 70.8%. Age, body mass index, and female sex were positively associated with the prevalence. Among the dietary factors, only vitamin K intake was shown to be inversely associated with the prevalence of radiographic knee OA by multivariate logistic regression analysis. The presence of joint space narrowing of the knee was also inversely associated with vitamin K intake. The prevalence of radiographic knee OA for each dietary vitamin K intake quartile decreased with the increased intake.CONCLUSIONS:

The present cross-sectional study using a population-based cohort supports the hypothesis that low dietary vitamin K intake is a risk factor for knee OA. Vitamin K may have a protective role against knee OA and might lead to a disease-modifying treatment.

Boston University School of Medicine, and Brigham and Women's Hospital, Boston, Massachusetts 02118, USA. tneogi@bu.eduAbstractOBJECTIVE:

Poor intake of vitamin K is common. Insufficient vitamin K can result in abnormal cartilage and bone mineralization. Furthermore, osteophyte growth, seen in osteoarthritis (OA), may be a vitamin K-dependent process. We undertook this study to determine whether vitamin K deficiency is associated with radiographic features of OA.METHODS:

We conducted an analysis among 672 participants (mean age 65.6 years, 358 women) in the Framingham Offspring Study, a population-based prospective observational cohort. Levels of plasma phylloquinone (the primary form of vitamin K) had previously been measured in these participants, for whom we also had bilateral hand and knee radiographs. The main outcomes were 1) prevalence ratios (PRs) of OA, osteophytes, and joint space narrowing (JSN) per quartile of plasma phylloquinone level for each joint, adjusting for correlated joints using generalized estimating equations, and 2) adjusted mean number of joints with each feature per quartile of plasma phylloquinone level. Analyses were conducted in hands and knees separately and adjusted for age, sex, body mass index, total energy intake, plasma vitamin D, and femoral neck bone mineral density.RESULTS:

The PRs for OA, osteophytes, and JSN and adjusted mean number of joints with all 3 features in the hand decreased significantly with increasing plasma phylloquinone levels (P<or=0.03 for all). For example, as plasma phylloquinone levels rose, the PR for hand OA decreased from 1.0 to 0.7 (P=0.005). For the knee, only the PR for osteophytes and the adjusted mean number of knee joints with osteophytes decreased significantly with increasing plasma phylloquinone levels (PR decreased from 1.0 to 0.6, P=0.01).CONCLUSION:

These observational data support the hypothesis of an association between low plasma levels of vitamin K and increased prevalence of OA manifestations in the hand and knee.